Flow-regulating device

ABSTRACT

1,128,613. Re-vaporizing liquefied gases. BRITISH OXYGEN CO. Ltd. 1 March, 1966 [15 March, 1965], No. 10863/65. Heading F4P. [Also in Division G3] In a heat-exchanger for the production of oxygen enriched air comprising a large number of small tubes mounted vertically between headers comprising upper and lower tube plates, previously cooled incoming air is passed in gaseous form over the lower part of the exchanger on the outside walls of the tubes which are retained at a sufficiently low temperature as to condense some of the air into a liquid mixture of oxygen and nitrogen which is subsequently fed into the top of each tube so that it trickles down the inside walls and is gradually evaporated by incoming air on the outside of the tubes. The cold produced by this evaporation serves to maintain the tube walls at the required low temperature. An adjustable flow regulating device (see Division G3) is fitted into each tube to ensure that the flow in any tube is kept within 10% of the average flow for all of the tubes.

Filed Feb. 28, 1966 FIG] F 3 INVENTOR MICHAEL Emvssr GARRETT ATTORNEYS United States Patent Office 3,429,342 Patented Feb. 25, 1969 3,429,342 FLOW-REGULATING DEVICE Michael E. Garrett, Addlestone, England, assignor to The British Oxygen Company Limited, a British company Filed Feb. 28, 1966, Ser. No. 530,307 Claims priority, application Great Britain, Mar. 15, 1965,

10,863/ 65 U.S. Cl. 13843 Int. Cl. Fd 1/02 1 Claim ABSTRACT OF THE DISCLOSURE The present invention relates to a flow regulating device which may be used to give an adjustable resistance to flow.

The device is particularly suitable for regulating the flow of fiuid into or out of a tube. A device of this kind may be used in distributing a liquid from a header into a plurality of vertical tubes, for example the tubes of a heat-exchanger of the condenser-evaporator type used in the production of oxygen-enriched air.

In a condenser-evaporator unit of this type a large number of small tubes are mounted vertically between headers comprising upper and lower tube plates. When the unit is used for the preparation of oxygen-enriched air, previously cooled incoming air is passed in gaseous form over the lower part of the unit on the outside walls of the tubes. These outside walls are maintained at a sufiiciently low temperature to condense some of the air into a liquid mixture of oxygen and nitrogen. This mixture is fed into the top of each tube so that it trickles down the inside walls of the tubes and is gradually evaporated by incoming air on the outside of the tubes. The cold produced by this evaporation serves to maintain the tube walls at the previously mentioned required low temperature.

For satisfactory operation, and in particular for efiicient heat exchange between the air and the liquid, an equal quantity of liquid should be fed into each tube at a throughput rate to ensure that the liquid runs down the inside wall of the tube in the form of a thin film. For this purpose weirs, or serrated or slotted tube ends, may be used, and the upper tube plate must be carefully levelled.

Even with these methods it is still difficult to obtain uniform distribution of the liquid, particularly if the upper tube plate departs even slightly from the horizontal. Any departure from uniformity is likely to become more marked under varying throughput; in particular, at low throughput rates irregular distribution can cause some of the tubes to run almost dry while in others a substantial volume of liquid passes through the tube unevaporated. The present invention provides a device which can be used to regulate the liquid fiow into each tube, so that by suitable adjustment thereof a high degree of uniformity in distribution can be achieved among all the tubes.

According to the present invention, there is provided a flow regulating device comprising an inner tubular member adapted to be fitted within an outer tubular member, and mens defining at least one circumferential flow passage between the tubular members when fitted together, the side wall of each tubular member being provided with at least one aperture communicating with the said flow passage in which the flow resistance of the flow passage between the apertures of the inner and outer tubular members may be varied by altering the relative positions of the apertures.

The means defining the flow passage may be a screw thread, conveniently formed on the external surface of the inner tubular member so that the threaded portion is a close fit within the outer tubular member. Preferably the apertures are in the form of longitudinal slits, the flow resistance between the slits being varied by turning one tubular member relatively to the other.

One of the tubular members may be an extension of a heat exchanger tube, or alternatively the two tubular members may form a unit which can be fitted onto a heat exchanger tube.

The invention will be further described with reference to the accompanying drawing, in which:

FIG. 1 shows a first embodiment of the invention as fitted to a heat exchanger tube,

FIG. 2 shows a second embodiment of the invention similarly fitted, and

FIG. 3 shows a third arrangement wherein an extension of the heat exchanger tube forms one of the tubular members.

Referring to FIG. 1 a fiow regulating device is shown fitted so as to regulate the flow from an upper tube plate 1 into a heat exchanger tube 2. The device comprises an inner tubular member '5 which is a push fit within an outer tubular member 6, and extends downwardly into the tube 2 to make a firm fit therewith. The inner and outer tubular members are provided with pairs of diametrically opposed slots 7 and 8 respectively, only one of each pair of slots being visible in the drawing. The slots 7 are open at their upper end and the slots 8 are open at their lower end. The inner tubular member 5 is also provided with an external screw thread the threads of which are a close fit within the outer member 6 so as to define therebetween a plurality of flow passages from the slots 8 to the slots 7.

In operation, liquid flowing over the tube plate 1 enters the slots 8, and flows along the flow passage provided by the screw thread 9 until it reaches the slot 7, through which it passes into the tube 2. The flow resistance through the flow passage is a function of its length, and this length can be adjusted by turning one tubular member relatively to the other thereby altering the distance between slots 7 and 8. It will be evident that for the device to ofier a flow resistance the slots 7 and 8 must not coincide.

FIGS. 2 and 3 show alternative arrangements which operate on the same principle as that of FIG. 1. In FIG. 2 the relationship between the inner and outer tubular members 5a and 6a is the same as in FIG. 1, but the combination is inverted and the outer member 6a fits within the heat exchanger tube 2a, being retained by a shoulder 10. In FIG. 3, the outer tubular member consists of an extension 612 of the heat exchanger t-ube 2b, which is slotted at 8b, and the inner tubular member 5b fits directly into this extension.

Experiments using this fiow regulating device Were carried out on a condenser-evaporator unit of the type used in the production of oxygen-enriched air. The unit had vertical tubes down which thin films of liquid were required to pass. Without the use of flow regulating devices it was found that there were considerable variations in the amount of liquid entering different tubes, some remaining almost dry while others took considerable flows. When each tube was fitted with the How regulating device described, it was found possible to adjust the devices so as to tune the individual tubes so that the flow in any tube was within 10% of the average flow for all the tubes.

Although the invention is particularly useful for condenser-evaporators, it may be applied to control the distribution of flow in tubes of any apparatus in which fluid is fed to vertical tubes from a header. While it is an advantage of the invention that the flow into individual tubes can be adjusted, if the device is accurately made little or no adjustment may be necessary.

It will normally be convenient to form the tubular members of the device from metal, such as brass or copper or stainless steel. It is envisaged however, that in some cases it might be advantageous to make the tubular members from extruded plastic tube, or to use plastic mouldings.

I claim:

1. A flow regulating device for regulating the flow of liquid into a substantially vertical tube comprising an outer tubular member, an inner tubular member adapted to be fitted within said outer tubular member, a screw thread formed on one of the tubular members so that the crests of the threaded portion make a close fit with the other tubular member to provide a plurality of flow passages between the tubular members, the side wall of each tubular member being provided with at least one longitudinal slit concurrently communicating with said plurality of flow passages in which the flow resistance of the flow passages between the slits of the inner and outer tubular members may be varied by rotating the tubular members relatively to one another.

References Cited UNITED STATES PATENTS 1,980,085 11/1934 Perry et al. 138-43 LAVERNE D. GEIGER, Primary Examiner.

BRADFORD KILE, Assistant Examiner. 

